There are a lot of 70s and 80s snake movies in the asian horror genre. Do you remember any specifics about the movie you are looking for? Is it a period piece or modern? Kung fu or just regular schmoes?
There is a good article about Snake women films in India and China here: http://www.illuminatedlantern.com/cinema/archives/snakes_and_snake_women.php
They also have reviews of several films in the genre.
The detatched head is another common motif in asia, but I don't have any good links at the moment because I lost them all when the laptop nuked itself. It doesn't sound like any of the main Mr. Vampire films, but could be one of the spinoffs or one of the Spooky Encounters spinoffs.